Compound beam mechanical casing collar locator

ABSTRACT

A mechanical casing collar locator is disclosed. The casing collar locator has an outermost, locator leaf spring cage, and one or more radially stacked reinforcement leaf spring cages. Each leaf spring cage has a plurality of flexible leaf spring beam members, each having a locator dog thereon for engage collar recesses, or other recesses, in the wellbore casing. The leaf spring beam members of the reinforcement leaf spring cages radially support the leaf spring beam members and the locator dogs of the locator leaf spring cage for providing enhanced radially outward spring force.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of patent application Ser. No. 15/052,663, filed Feb. 24, 2016, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/120,261, filed Feb. 24, 2015, the entirety of each of which is incorporated herein by reference.

FIELD OF THE DISCLOSURE

Embodiments herein relate generally to apparatus and methods for detection of casing collars in a casing string for positioning of wellbore tools relative thereto, and in particular to a mechanical casing collar locator.

BACKGROUND

In the process of wellbore completion, a string of casing is typically run into an open borehole and is cemented into place. Various downhole components can be located along the casing, including sleeve valves for access to a formation of interest. A downhole tool can be run into the casing string on a conveyance string and the tool is located at specific downhole components by feedback from a locater positioned on the tool. The locator detects the component itself, or another feature on the casing, such as collars that can be spacially related to the position of the component. It is important that the tools are locatable at known and desired locations within the casing for performance of well operations, including actuation of the downhole components in the string of casing.

In conventional embodiments, the casing comprises lengths or joints of tubing which are connected by threaded collars. Ends of the axially aligned joints of casing are threaded into the collars. Once threaded therein, the ends of the casing do not abut, leaving an axial space therebetween. The axial space or recess formed in the collar has a greater radial dimension than a bore of the joints of casing, forming a locatable feature in the casing string. Alternatively, where casing connections do not provide such a gap, specially designed locator tubulars or collars having a recess formed therein may be installed in the casing string for the express purpose of location.

As is also known, locators can be used not only to detect the collar gap or recess, but can be used to locate any suitable recess or profile in the string of casing, which may be formed at the downhole component, such as a sleeve valve. For example, a suitable profile can be formed at an end of a shifting sleeve movable therein.

A variety of apparatus are known to locate the collars within the casing string to better understand the positioning of tools run into the wellbore relative to the casing component. Known casing collar locators include those using electronic or magnetic sensors in an attempt to consistently locate the collars.

Other known locators are mechanical locators which comprise arrangements of radially extending, biased members, including protruding dogs, which releasably engage a respective axial space along the casing string. Once engaged in the collar or other recess, axial load or weight at surface on the downhole tool is resisted by the locater engagement in the recess, the shift in load or weight to the conveyance string being observable at surface as an indication of having reached the desired location.

The reliability of location using mechanical locators is generally related to the resolvable change in the force applied to the tool's conveyance string during movement. When the locator engages a recess, a certain axial force is required to dislodge the locator therefrom. If the locator engages the recess during a running in stage, an increased downhole force is required to dislodge it from the recess. If the locator engages the recess during a pulling out of hole stage, an increased uphole force is required to dislodge it from the recess. The increased force is measured by a change in the surface weight of the conveyance string. Typically, when running in using coiled tubing, lifting weight is used as a marker of locator positioning, and thus, the nature of the locator/recess interaction is designed for release of the locater from the recess during pulling out. Others may use a reduction in weight or a pushing force and, in those instances, the nature of the locator/recess interaction is designed for release of the locater from the recess during running in.

The release force is a function of a radially outward, recess-engagement force and a ramping interface of the locator and recess interface. The recess has uphole and downhole edges and the locator has leading and trailing ramp surfaces. Pulling or pushing of the tool and locator forms axial loading of the locator ramp against a recess edge. The interface imposes a radially inward release force on the locator, resisted by a biasing of the locator.

The mechanical advantage of a shallow or small interface angle produces large, radially inward force with small axial applications of weight, resulting in relatively indistinguishable weight change and poor locator resolution. A steep or large interface angle produces a small radially inward force, even at large axial applications of weight, providing easily detectable weight changes but at a risk of non-release of the locator and a stuck tool and/or erratic performance.

For example, FIG. 1 is a portion of a cross-sectional view of a prior-art mechanical casing collar locator 10 with a locator dog 12 located in a collar recess 14 formed by a collar 16 and adjacent casing joints 18 and 20. The locator dog 12 is profiled, having an uphole ramp or interface 22 and a downhole ramp or interface 24. The dog 12 is typically driven outward with a spring. The spring force, and ramp, determines the release behavior of the dog 12 from the recess 14.

As described above, the interface angle significantly affects the performance of the casing collar locator. In this example, the uphole interface 22 has an interface angle θ greater than 60 degrees with respect to a direction 26 parallel to the axis of the casing 18. Consequently, the radial spring force Fs required to maintain the locator dog in the recess is relatively small. However, a large uphole force Fp is required to pull the locator dog 12 out of the recess 14.

It is believed that the release behavior or predictability of a locator dog having an interface angle greater than 60 degrees can become erratic due to the requirement of a large release force for releasing the locator dog out of the collar recess, even if the radial spring force is small. As the interface angle becomes larger, even up to 90 degrees, the locator dog becomes stuck.

At 60 degrees or smaller, release is much more predictable, however in order to provide a visual indication at surface, the spring force must be quite high. Ideally, the interface and biasing force are complementary to provide sufficient weight change for consistent detection of locator engagement, yet not so great as to risk tool entrapment or a non-consistent release force.

Given the risk of entrapment or poor detection resolution, there is still room for improvement to locator technology.

SUMMARY

Given that tool entrapment is highly undesirable, the designed interface angles at the locator and recess are usually shallow and therefore robust radial biasing is required to provide engagement indication. Biasing is typically associated with the spring material selection and dimensions. Given limited selections in material, the industry typically employs larger springs for applying more force. Larger springs, coil springs or spring beams, require a significant portion of the tool cross-section. If smaller robust springs are required, material properties need to be increased, however only at the risk of limited elastic displacement before entering the plastic range of deformation. Further, springs such as coil springs are prone to trapping of debris therein which may affect tool performance.

In conventional downhole tools, the cross-section typically includes fluid passageways and apparatus, including equalization valves, sliding members and the like. Robust locators, having structure to provide high radial engagement biasing, can interfere with the sizing and placement of tool components and thus the strength of the biasing is generally limited. Known prior art apparatus have such restricted diametrical area, and the integration of a locator in such an environment limits the biasing strength. Such restrictions can compromise the radial force needed to achieve a pull-through force which is high enough to be consistently detected and ensure positive and reliable location. In Canadian Patent Application No. 2,693,676 to NCS Oilfield Services Inc., the locator is physically positioned in the tool to reside within the sleeve valve, such as to engage ends of the tubular sleeve. The tool is fit with fluid passageways to conduct fluid across the tool, including through the locator. A spring-loaded dog locator is provided having a locator body, dogs and coil springs between the dogs and the body for urging the dogs radially outwardly. The body structure occupies a significant portion of the tool cross-section and thus, the spring aspect is minimized, limiting the biasing force possible. Further, with respect to published patent application CA 2,856,184 to NCS Oilfield Services Inc., a locator comprising a leaf spring cage having dog formed thereon is positioned concentrically about at least a J-slot arrangement. The J-slot arrangement occupies a significant portion of the tool cross-section and thus, the spring aspect is also minimized, limiting the biasing force possible.

Solutions to constraints on the spring can, to a certain extent, be managed with changes to spring material or spring thickness, however, this is also associated with reduced elastic range and potential for reduced fatigue life or even plastic deformation. Further, attempts to counter reduced radial biasing forces by increasing the interface angle increases the risk of tool entrapment or inconsistent release loads.

According to one aspect of this disclosure, there is provided an apparatus for locating an annular recess along a wellbore string. The apparatus comprises: a plurality of circumferentially-spaced, radially outwardly extending dogs for engaging the recess; and a plurality of supporting structures for supporting the plurality of dogs; wherein each supporting structure comprises: two or more radially stacked layers of circumferentially-spaced, radially flexible, leaf spring beam members extending along an axial direction.

In some embodiments, each dog comprises a first interface for engaging an edge of the recess, the first interface being angled from the axial direction at a first interface angle of about or less than 60 degrees.

In some embodiments, the first interface angle is about 50 degrees.

In some embodiments, the first interface is an uphole interface.

In some embodiments, at least a first layer of the two or more layers of circumferentially spaced leaf spring beam members form a locator cage.

In some embodiments, the locator cage is a slotted tubular.

In some embodiments, the circumferentially spaced leaf spring beam members of the locator cage are supported at at least one of two axially opposite ends thereof by a solid tubular portion.

In some embodiments, the circumferentially spaced leaf spring beam members of the locator cage are supported at each of two axially opposite ends thereof by a solid tubular portion.

In some embodiments, the at least first layer is the radially outmost layer, and wherein at least a second layer of the two or more layers of circumferentially spaced leaf spring beam members form a reinforcement cage.

In some embodiments, the reinforcement cage is a slotted tubular.

In some embodiments, the circumferentially spaced leaf spring beam members of the locator cage are supported at at least one of two axially opposite ends thereof by a solid tubular portion.

In some embodiments, the circumferentially spaced leaf spring beam members of the locator cage are supported at each of two axially opposite ends thereof by a solid tubular portion.

In some embodiments, the reinforcement cage is concentrically received in the locator cage.

In some embodiments, each dog is supported by at least one beam member of the first layer, and each beam member of the first layer is supported by at least one beam member of the at least second layer.

In some embodiments, the locator cage further comprises a first coupling mechanism at an uphole end thereof for coupling the locator cage to a first sub and a second coupling mechanism at a downhole end thereof for coupling the locator cage to a second sub.

In some embodiments, after the locator cage is coupled to a first sub at the uphole end thereof and to a second sub at the downhole thereof, the at least first reinforcement cage is axially fixed or axially moveable within a predefined range.

In some embodiments, the two or more radially stacked layers of leaf spring beam members are radially aligned.

In some embodiments, the reinforcement cage is circumferentially fixed with respect to the locator cage.

In some embodiments, the apparatus further comprises: a delimit pin extending from the reinforcement cage radially outwardly into a slot between two adjacent positioned in a slot between two adjacent spring beam members of the locator cage, for preventing the reinforcement cage from rotating with respect to the locator cage.

According to another aspect of this disclosure, there is provided an apparatus for locating an annular recess along a wellbore string. The apparatus comprises: a tubular locator cage having a plurality of circumferentially-spaced, radially flexible, locator leaf spring beam members extending along an axial direction, each locator leaf spring beam member having a locator dog thereon and extending radially outwardly, the locator cage having a locator bore; and at least a first tubular reinforcement cage fit concentrically within the locator bore, each of the at least a first tubular reinforcement cage having a plurality of circumferentially-spaced, radially flexible, reinforcement spring beam members extending along the axial direction and for supporting the locator leaf spring beam members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a portion of a cross-sectional view of a prior-art casing collar locator having a dog thereon engaging a casing collar recess, the dog having an uphole interface with a relatively large interface angle greater than 60 degrees, resulting in a requirement of a large uphole pulling force to pull the dog from the recess, and resulting in risk of trapping of the dog in the recess;

FIG. 2 is a perspective view of an assembled casing collar locator, according to an embodiment;

FIG. 3 is an end view of the casing collar locator of FIG. 1, showing an outmost, locator leaf spring cage and two reinforcement leaf spring cages being arranged concentrically;

FIG. 4 is a perspective view of a partially assembled casing collar locator with the locator leaf spring cage and two reinforcement leaf spring cages being axially offset, the leaf spring beam members of the locator leaf spring cage and two reinforcement leaf spring cages being aligned;

FIG. 5 is a perspective view of the locator leaf spring cage;

FIG. 6 is an end view of the locator leaf spring cage of FIG. 5;

FIG. 7 is a cross-sectional view of the locator leaf spring cage of FIG. 5;

FIG. 8 is a perspective view of a reinforcement leaf spring cage;

FIG. 9 is a cross-sectional view of the reinforcement leaf spring cage of FIG. 8;

FIG. 10 is a cross-sectional view of the casing collar locator of FIG. 1;

FIG. 11 is a portion of a cross-sectional view showing the casing collar locator of FIG. 1 engaging a collar recess;

FIG. 12 is an enlarged view of portion A of FIG. 11, showing an uphole interface of a dog engaging an uphole edge of the collar recess;

FIG. 13 is a perspective view of the locator leaf spring cage, according to some alternative embodiments;

FIG. 14 is a perspective view of a reinforcement leaf spring cage, according to some alternative embodiments; and

FIG. 15 is a perspective view of the locator leaf spring cage, according to some other embodiments.

DETAILED DESCRIPTION

Various embodiments of a mechanical casing collar locator are disclosed herein, comprising an outermost, locator leaf spring cage, and one or more radially stacked reinforcement leaf spring cages. Each leaf spring cage comprises a plurality of circumferentially-spaced, flexible, leaf spring beam members. Each flexible leaf spring beam member of the locator leaf spring cage comprises a locator dog formed to extend radially outwardly from an intermediate position thereof. The reinforcement leaf spring cage radially supports the locator leaf spring cage for providing enhanced radially outward spring force.

Each locator dog is a profiled dog, extending radially outwardly from each flexible leaf spring beam member of the locator leaf spring cage so as to engage collar recesses, or other recesses, in the wellbore casing. The profiling includes uphole and downhole interfaces or ramps, the selected angle of which is discussed below for adjusting pull-through forces in combination with the recess.

The resulting casing collar locator provides significant radially outward directed engagement force (i.e., a force of a direction perpendicular to and pointing away from an axis of the casing collar locator), enabling a reduction in the interface angle of an engagement interface of each of one or more profiled dogs, such that, the profiled dogs of the casing collar locator can engage a collar recess with a low risk of tool entrapment and higher weight resolution at surface for consistent detection of casing collar recesses. The casing collar locator disclosed herein achieves high engagement force while able to use a minimum of the locator cross-section, or simply provide significantly higher radial biasing forces while remaining within the elastic range of operation of the biasing with the radial range of displacement required to enter and exit casing recesses.

In embodiments, the present locator achieves sufficient outwardly directed radial force therein, such that an angle of an uphole interface or ramp of a profiled dog formed thereon is maintained at an angle below that at which erratic pull-through force could occur. In combination, the strong radial force and dog interface angle achieve an optimum pull-through force, such as about 3000-4000 dN, for positive, consistent and reliable location. The pull-through force can also be varied from tool to tool, such as depending upon the number of spring cages utilized.

Thus, in addition to the ability to provide suitable engagement force with low interface angles for restricted diametrical environments, further advantage is obtained where larger diametrical extent is available, and greater weight resolution can be achieved at surface. The casing collar locator disclosed herein is particularly useful for tool strings which are arrange to position the locator therein away from other internal apparatus so as to provide maximum diametric space therein. Generally, if the locator is used to locate a casing collar spaced axially from a shifting sleeve, rather than to the end of the shifting sleeve as known in the prior art, the locator can be spaced below other apparatus in the tool string where increased diametrical area is available therein to accommodate the locator disclosed herein and maximize the release resolution. Embodiments disclosed herein can locate within a sleeve, however the sleeve length must be adjusted accordingly.

Thus, the locator disclosed herein may be used in various scenarios. For example, in some embodiments, a downhole tool may comprise a bottom hole assembly (BHA) coupled to the locator disclosed herein. The locator comprises a bore forming a flow path, which is in fluid communication with a flow path of the BHA.

Turning now to FIGS. 2 to 4, a mechanical casing collar locator is shown, and is referenced using numeral 100. Similar to traditional casing collar locators, the collar locator 100 may be coupled to, at either or both ends thereof, suitable subs 106 such as a crossover sub, and is used for locating one or more locator recesses of a casing string such as at collar recesses 14. The one or more collar recesses 14 are formed as described above, and each collar recess has a recess diameter.

As shown, the collar locator 100 is a beam-type locator having a tubular locator leaf spring cage 102 with a bore for receiving therein one or more concentrically arranged, stacked reinforcement leaf spring cages 104. FIG. 4 shows a partially assembled locator leaf spring cage 102 and two reinforcement leaf spring cages 104A and 104B, axially offset for better illustration.

As shown in FIGS. 5 to 7, in this embodiment, the locator leaf spring cage 102 comprises a tubular housing 110 having a bore formed therethrough. The housing 110 is machined to form a plurality of circumferentially and alternately arranged slots 108 and resilient, leaf spring beam members 112 (denoted as locator leaf spring beam members 112), extending along an axial or longitudinal direction. Therefore, the locator leaf spring beam members 112 are spaced from each other, and are separated by the slots 108.

Each leaf spring beam member 112 comprises a radially outwardly extending dog 114 formed intermediate therealong. For example, in FIGS. 5 to 7, eight (8) leaf spring beam members 112 are formed, each having an integrated, radially outwardly extruded dog 114 located at about a mid-point of the corresponding leaf spring beam member 112. The leaf spring beam members 112 are made of metal material with suitable elasticity to provide required radial flexibility for dogs 114 to enter and exit the recess 14.

In this embodiment, each slot 108 terminates at an end 112A/112B spaced axially inwardly from each opposing end of the housing 110, leaving a rigid, solid tubular portion 118 at opposing ends of the locator leaf spring cage 102. The tubular portion 118 supports the ends 112A and 112B of each beam member 112, and provides a structure for retaining the beam members 112 in axial and circumferential alignment.

In an unbiased position, the diameter about the dogs 114 is greater than that of the inside diameter of the casing, and corresponds more to a diameter of, or larger than that of, the circumferential collar recess. Accordingly, the dogs 114 drag along the casing string, biased to enter any recess therealong. The radially stacked leaf spring beam members 112 exert a radial spring drag force to bias the dogs 114. The greater the number of stacked layers of leaf spring beam members 112, the greater the aggregated radial spring drag force.

Referring to FIG. 7, the dog 114 of each leaf spring beam member 112 is profiled, having an uphole locator ramp or interface 122 and a downhole locator ramp or interface 124. The interface angles α and β of the locator interfaces 122 and 124, respectively, with respect to a direction parallel to the longitudinal axis of the locator leaf spring cage 102 are chosen to be relatively small angles, depending on the design requirements. For example, in the embodiment shown in FIG. 7, the casing collar locator 100 is used for locating collar recesses during a pull-out-of-hole stage. Therefore, the downhole interface is angled such that the downhole tool including the casing collar locator 100 can be readily run in and moved downhole along the casing and past the recesses therein. For example, the downhole interface angle β in this example is a relatively small angle such as about 15 degrees for ease of insertion of the locator into the casing. The uphole interface angle α may be an angle suitable for a sufficiently high resolution to locate a collar recess with sufficient accuracy, e.g., about 60 degrees or smaller.

In this embodiment, the locator leaf spring cage 102 also has a plurality of screw holes 116 on each ends thereof for locking the casing collar locator 100 to suitable subs (not shown).

To provide the radial range of motion, while maintaining the radially elastic deflection of the locator leaf spring cage 102, one or more concentrically arranged, stacked reinforcement spring cages 104 are provided.

As shown in FIGS. 8 and 9, the structure of the reinforcement spring cage 104 is similar to that of the locator leaf spring cage 102. In particular, the reinforcement spring cage 104 comprises a tubular housing 130 having a bore formed therethrough. The housing 130 is machined to form a plurality of circumferentially and alternately arranged slots 132 and resilient, leaf spring beam members 134 (denoted as reinforcement beam members 134), extending along a longitudinal direction. At least the leaf spring beam members 134 are made of metal material with suitable elasticity to provide required radial flexibility. However, in this embodiment the leaf spring beam members 134 do not comprise any radially outward protrusion.

In this embodiment, the number of leaf spring beam members 134 of each reinforcement spring cage 104 can correspond to that of the leaf spring beam members 112 of the locator leaf spring cage 102 such that each locator leaf spring beam member 112 is supported by at least one reinforcement beam member 134 to reinforcing the biasing thereof.

Similar to the slots 108 of the locator leaf spring cage 102, each of the slot 132 of the reinforcement spring cage 104 terminates spaced axially inwardly from each opposing end of the housing 130, leaving a rigid, solid tubular portion 138 at opposing ends of the reinforcement spring cage 104 for providing fixed supports at the end of each beam member 134 and a structure for retaining the beam members 134 in axial and circumferential alignment.

In this embodiment, each reinforcement spring cage 104 also comprises an alignment port 136 axially spaced from a slot 132 for receiving an alignment pin (described later).

The outer diameters of the reinforcement spring cages 104 are such that each reinforcement spring cage 104 fits concentrically within the bore of an adjacent outer spring cage, which may be the locator leaf spring cage 102 or an outer reinforcement spring cage 104.

In this embodiment, each reinforcement spring cage 104 has a length shorter than that of the locator leaf spring cage 102 to allow the locator leaf spring cage 102 to receive other subs extending thereinto for coupling thereto.

As described above, a casing collar locator 100 may be assembled using a locator leaf spring cage 102 and one or more reinforcement spring cages 104. In an example shown in FIGS. 2 to 4 and 10, a casing collar locator 100 is assembled using a locator leaf spring cage 102. Concentrically received within the locator cage 102 are two reinforcement spring cages 104A and 104B, with the spring cage 104B received within the spring cage 104A. As shown in FIG. 4, the spring cages 102, 104A and 104B are circumferentially aligned such that the slots 108 and 132 thereof are aligned and the leaf spring beam members 112 and 134 are also aligned.

After the spring cages 102, 104A and 104B are axially in position (see FIGS. 1 and 10), the alignment ports 136 of the reinforcement spring cages 104A and 104B are also aligned. As the lengths of the two reinforcement spring cages 104A and 104B are shorter than that of the locator leaf spring cage 102, the alignment ports 136 thereof are exposed through a slot 108A of the locator leaf spring cage 102. As shown in FIG. 1, a delimit pin 140, such as a socket head cap screw, extends through the slot 108 a and is secured into the alignment ports 136 of the reinforcement spring cages 104A and 104B. The head of the pin 140 projects from the cage 105A to be circumferentially constrained within the slot 108A to prevent relative rotation between the spring cages 102, 104A and 104B so as to maintain the radially stacked alignment of the leaf spring beam members 112 and 134.

As persons skilled in the art appreciate, the aligned slots 108 and 132 in the concentric spring cages 102 and 104 can also provide fluid pathways therethrough, such as to a bore of the locator and tool string. Such fluid pathways are useful in flushing debris therethrough.

After assembling, the reinforcement spring cages 104A and 104B are circumferentially constrained, but are allowed to move or slide axially. For ease of storage and transportation, the assembled casing collar locator 100 may be capped at both ends thereof to prevent the inner, reinforcement spring cages 104A and 1046 from moving out of the outer, locator spring cage 102.

As shown in FIG. 10, in use, the assembled casing collar locator 100 is coupled to subs 106A and 106B on the uphole and downhole ends thereof. As shown, the outermost, locator leaf spring cage 102 comprises inwardly threaded ends, operatively connected to outwardly threaded respective ends of subs 106A and 106B. The connections of the locator leaf spring cage 102 and subs 106A and 1066 are further secured by the screws 142 screwing through the holes 116 of the locator leaf spring cage 102 and onto the respective subs 106A and 106B. Of course, other known methods of coupling the locator leaf spring cage 102 to subs 106A and 1066 are also readily available and may be alternatively used.

After coupling the locator leaf spring cage 102 to subs 106A and 106B, the reinforcement spring cages 104A and 104B are then axially sandwiched between the subs 106A and 106B, with the opposite ends of the reinforcement spring cages 104A and 104B loosely facing the butt ends of subs 106A and 106B. The axial location of the reinforcement spring cages 104A and 1046 is thus delimited by the subs 106A and 106B respectively at the uphole and downhole sides thereof.

As the spring cages 102, 104A and 104B have the same number of leaf spring beam members 112, 134, and are aligned circumferentially, after assembly, the leaf spring beam members 112, 134 of the spring cages 102, 104A and 104B are radially aligned and stacked “on top of one another”. As will be described in more detail below, the stacked leaf spring beam members 112, 134 provide higher radial spring force Fs for maintaining the locator dogs 114 in the collar recess.

As described above, in a radially unbiased position, the diameter about the dogs 114 is greater than that of the inside diameter of the casing. In some embodiments, the diameter about the dogs 114 is about, or even larger than, a diameter of the circumferential collar recess. While running in, each dog 114 and the corresponding leaf spring beam member 112 are deflected radially inward to a smaller diameter, such as the inner diameter of the casing or the downhole component or sleeve. Any axial length change due to the radial deflection of the spring cage 102 is reflected in a change in the axial spacing of the subs 106A and 106B. However, any change of axial length of the reinforcement cages 104A and 104B are unconstrained as the delimit pin 140 can move axially in slot 108A, and thus the reinforcement cages 104A and 104B can float axially between subs 106A and 106B.

The inward, elastic deflection of the leaf spring beam member 112 of the outmost locator leaf spring cage 102 urges and inwardly and elastically deflects the radially stacked, one or more leaf spring beam members 134 of the one or more inner, reinforcement spring cages 104. As the corresponding leaf spring beam members 112 and 134 are not mounted together, they can deflect radially and can shift axially with respect to each other. Comparing to the embodiment of a locator cage having “thick” leaf spring beam members but with no reinforcement cages, the above design shown in FIG. 10 allows larger elastic range. Comparing to the embodiment that the reinforcement cage(s) 104 are also axially fixed to the locator cage 102 (described later), the above design shown in FIG. 10 avoids stress caused by different deflections and/or different length changes of the leaf spring beam members 112 and 134.

As each leaf spring beam member 112 of locator leaf spring cage 102 is elastically supported radially by the respective leaf spring beam members 134 of the one or more inner, reinforcement spring cages 104, the total radially outwardly directed spring force Fs is an aggregated radial spring force exerted by the stacked leaf spring beam members 112 and 134. For example, in the embodiment of FIG. 10, the casing collar locator 100 comprises three spring cages 102, 104A and 104B, and the outward radial force Fs is much larger than that of a single spring cage 102, 104A or 104B. Those skilled in the art appreciate that an estimate or calculation of the radial force Fs is readily available using known theories.

When the dogs 114 move into a collar recess, the radially outward force Fs causes the dogs 114 and the leaf spring beam members 112 and 134 to return towards their normal, radially unbiased positions.

FIG. 11 is an illustration showing a portion of the casing collar locator 100 being pulled uphole and having engaged a collar recess 14 formed by a casing collar 16 between two adjacent casing joints 18 and 20. The aggregated force Fs allows the casing collar locator 100 to provide higher recess detection resolution (or weight resolution if using weigh change as an indication of detection) at surface.

As shown in FIGS. 11 and 12, when the tubing string and therefore the casing collar locator 100 is again pulled uphole by an uphole force Fp, the edge 152 of the collar recess 14 pushes the uphole locator interface 122 of the dog 114 engaged therewith, with a force Fr perpendicular to the plane of the uphole locator interface 122. The force Fr corresponds to an axially downhole force Fd combatting the pulling force Fp, and a radially inward force Fi combatting the radially outward spring force Fs to urge the leaf spring beam members 112 and 134 to deflect radially inwardly against the combined or aggregated beam biasing.

As described above, the angle α of the uphole locator interface 122 is relatively small, e.g., about or smaller than 60 degrees. However, by reinforcing the dog 114 with two or more leaf spring beam members 112 and 134 to obtain an aggregated radial spring force Fs, a large force is then required to pull the dog 114 out of the recess, giving rise to a higher weight resolution at surface for recess detection.

Further, at about 60 degrees or less, risk of jamming between the uphole locator interface 122 and the edge 152 of the collar recess 14 and/or tool entrapment is minimized. In some embodiments, the uphole locator interface 122 may be angled at about 50 degrees. The degree of angle of the uphole locator interface 122 can be balanced with the number of stacked spring cages 102 and 104 to provide the desired pull-through force to achieve reliable location. With the above described casing collar locator 100, locating a collar recess 14 by the casing collar locator 100 can be consistently observed at surface, and the profiled dog 114 can also be reliably disengaged and removed from the recess 14.

As a comparison, the traditional mechanical casing collar locator 10 of FIG. 1, assuming that it is manufactured using the same material as the casing collar locator 100 disclosed herein, provides a smaller spring force Fs. Consequently, a large interface angle α, e.g., larger than 60 degrees and up to 90 degrees, is needed to provide sufficient weight resolution at surface. However, such a large interface angle α has a high risk of jamming and/or entrapment.

In a process for locating a casing collar recess 14, the tool string, having the casing collar locator 100 positioned therein, is deployed into the wellbore, such as on coiled tubing. The tool string is run into the wellbore below a depth at which the operator anticipates a collar of interest to be located as is well understood in the art. The tubing string is then lifted until the profiled dogs 114 reach the collar recess 14 at which time the deflected, stacked spring cages 102 and 104 are able to release and apply the radial outwardly force, resulting in positive engagement of the profiled dogs 114 within the recess 14. As the dogs 114 engage in the recess 14, weight applied to the coiled tubing is transferred to the casing which can be observed at surface. When the tool string is to be moved within the wellbore, a pulling force Fp is applied to the coiled tubing string. At the design pull-through force, for example at about 3000-4000 daN (Decanewton), the profiled dogs 114 are pulled out of the recess 14 and the tool can thereafter be moved within the wellbore.

In some alternative embodiments, the collar recess 14 may also have angled uphole and/or downhole edges, and the angles of the uphole and/or downhole locator interface 122, 124 may be selected to mate the angles of uphole and/or downhole edges, respectively.

In above embodiments, the uphole interface angle α is larger than the downhole interface angle α. However, those skilled in the art appreciate that the uphole and downhole angles α and β may be any suitable values. For example, in some alternative embodiments, the uphole and downhole interfaces 122 and 124 have the same interface angle, i.e., α=β, and in some other embodiments, the uphole interface angle α may be smaller than the downhole interface angle β.

Referring again to FIGS. 7 and 10, in above embodiments, the leaf spring beam members 112 of the locator leaf spring cage 102 are also profiled at an inner surface thereof beneath the respective dogs 114, forming discontinuous areas or points of contact between the leaf spring beam members 112 of the locator leaf spring cage 102 and the leaf spring beam members 134A of the adjacent reinforcement leaf spring cage 104A.

In some alternative embodiments, the leaf spring beam members 112 of the locator leaf spring cage 102 are not profiled at the inner surface thereof (in other words, having a local, thicker cross-section at the dog location), and are in contact with the leaf spring beam members 134A of the adjacent reinforcement leaf spring cage 104A substantially along their entirety.

In some other embodiments, the leaf spring beam members 112 of the locator leaf spring cage 102 are profiled at the inner surface thereof. Correspondingly, the leaf spring beam members 134A of the adjacent reinforcement leaf spring cage 104A are also profiled accordingly such that the leaf spring beam members 112 are in contact with corresponding leaf spring beam members 134A thereunder substantially along their entirety.

In above embodiments, the leaf spring beam members 112 and 134 of the locator leaf spring cage 102 and reinforcement leaf spring cage(s) 104, respectively, are supported at both ends 112A and 112B thereof.

In some alternative embodiments as shown in FIG. 13, the leaf spring beam members 112 may be supported only at one end 112A thereof by a solid tubular portion 118, being cantilevered therefrom. In such cantilevered embodiments, additional spring force Fs may be required compared to the above described embodiments to achieve the design pull-through force. Additional concentric reinforcement leaf spring cages 104 or other types of springs may be added to increase the spring force.

Similarly in some alternative embodiments as shown in FIG. 14, the leaf spring beam members 134 may be supported only at one end 134A thereof by a solid tubular portion 138, being cantilevered therefrom.

In some alternative embodiments as shown in FIG. 15, some leaf spring beam members 112-1 may be supported only at one end 112A thereof by a solid tubular portion 118A, being cantilevered therefrom, and other leaf spring beam members 112-2 are supported at both ends 112A and 112B thereof by solid tubular portions 118A and 118B, respectively. Similarly, in some alternative embodiments, some of the leaf spring beam members 134 may be supported only at one end thereof by a solid tubular portion, being cantilevered therefrom, and others of the leaf spring beam members 134 are supported at both ends thereof by solid tubular portions, respectively.

In above embodiments, the leaf spring beam members 112 and 134 of the locator leaf spring cage 102 and reinforcement leaf spring cage(s) 104, respectively, are radially aligned, and each of the leaf spring beam members 112 and 134 (except those of the innermost reinforcement leaf spring cage) is supported by one leaf spring beam member 134 thereunder. In some alternative embodiments, at least one of the leaf spring beam members 112 and/or 134 is supported by two or more leaf spring beam members 134 thereunder. For example, at least one reinforcement leaf spring cage may be misaligned with the (locator or reinforcement) leaf spring cage adjacent and radially outward thereof such that each leaf spring beam member of the outer leaf spring cage is supported by two leaf spring beam members of the inner leaf spring cage.

In above embodiments, each leaf spring cage comprises a same number of leaf spring beam members. In some alternative embodiments, at least one leaf spring cage comprises a different number of leaf spring beam members.

In above embodiments, the leaf spring cages 102 and 104 are circumferentially fixed to each other by a delimit pin 140. In some alternative embodiments, at least some of the leaf spring cages 102 and 104 are not circumferentially fixed such that they may rotate and circumferentially misaligned.

In above embodiments, each dog 114 is an integrated part of the respective leaf spring beam member 112 formed by outwardly extending a mid-portion of the leaf spring beam member 112. In some alternative embodiment, at least some dogs 114 are manufactured separately, and then each dog 114 is mounted to an outer surface of the respective leaf spring beam member 112 using suitable means such as welding, screwing and the like.

In above embodiments, the dogs 114 are at about a mid-point of their respective leaf spring beam members 112. In some alternative embodiments, the dogs 114 are at a point axially offset from the mid-point of the respective leaf spring beam members 112.

In some alternative embodiments, some leaf spring beam members 112 of the locator leaf spring cage 102 may not comprise any dogs.

In some alternative embodiments, the spring cages 102 and 104 are also axially fixed to each other using suitable fastening means, e.g., screws.

In the casing collar locator 100 disclosed herein, each dog 114 is supported by two or more leaf spring beam members 112 and 134, i.e., directly supported by a locator leaf spring beam member 112 and further reinforced by one or more reinforcement leaf spring beam members 134. In above embodiments, the casing collar locator 100 comprises a locator spring cage 102 for forming the locator leaf spring beam members 112, and one or more reinforcement spring cage 104 for forming the reinforcement leaf spring beam members 134.

In some alternative embodiments, the casing collar locator 100 comprises a locator spring cage 102 for forming the locator leaf spring beam members 112 for directly supporting the dogs 114. However, the casing collar locator 100 does not comprise any reinforcement spring cage 104. Rather, one or more laminated, reinforcement leaf spring beams each having one or more layers of leaf spring beam members 134 is coupled to each locator leaf spring beam member 112 by using suitable fasteners. The reinforcement leaf spring beam may be circumferentially constrained, but may be allowed to move axially within a predefined range. The laminated, reinforcement leaf spring beams may be coupled to the inner surface, outer surface or both surfaces of the locator leaf spring beam member 112, as needed or desired.

In above embodiments, after the locator leaf spring cage 102 is coupled to a first and a second subs 106 at the uphole and downhole ends thereof, respectively, the reinforcement leaf spring cage(s) 104 are axially fixed in a predefined position. In some alternative embodiments, after the locator leaf spring cage 102 is coupled to a first and a second subs 106 at the uphole and downhole ends thereof, respectively, the reinforcement leaf spring cage(s) 104 may still be axially moveable within a predefined range.

Although embodiments have been described above with reference to the accompanying drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the scope thereof as defined by the appended claims. 

What is claimed is:
 1. Apparatus for coupling with a downhole tool, the apparatus releasably locating an annular recess along a casing string in a wellbore, comprising: a tubular locator cage, adapted for coupling to the downhole tool, having a tubular housing having opposing ends, a locator bore, and a plurality of radially flexible locator leaf spring beam members extending along an axial direction from each opposing end and spaced circumferentially from each other by locator slots, each locator slot terminating axially inward of the housing's opposing ends, each locator leaf spring beam member having a locator dog extending radially outwardly therefrom and intermediate therealong for engaging the annular recess; at least a first tubular reinforcement cage fit concentrically within the locator bore, each reinforcement cage having a plurality of radially flexible reinforcement spring beam members extending along the axial direction, spaced circumferentially from each other by slots, wherein each reinforcement cage being retained in the locator bore in axial arrangement wherein that each locator leaf spring beam member is supported by at least one reinforcement beam member for providing an aggregated radial spring force at the locator dogs.
 2. The apparatus of claims 1 further comprising: an uphole sub connected to an uphole end of the locator cage; and a downhole sub connected to a downhole end of the locator cage.
 3. The apparatus of claim 1 wherein each reinforcement cage is delimited within the locator bore in axial arrangement between the uphole sub and the downhole sub.
 4. The apparatus of claim 1 wherein each reinforcement cage has a tubular housing having opposing ends and a bore.
 5. The apparatus of claim 4 wherein at least a second reinforcement cage is fit concentrically within the bore of the first reinforcement cage and in axial arrangement therewith.
 6. The apparatus of claim 1 wherein each reinforcement cage has an axial length shorter than the axial length of the locator cage wherein the reinforcement cage's opposing ends are exposed through the locator slots for securing a delimit pin therethrough and maintaining circumferential arrangement of the spring beam members of the locator cage and each reinforcement cage.
 7. The apparatus of claim 1 wherein each dog comprises a first interface for engaging an edge of the recess, the first interface being angled from the axial direction at a first interface angle of about 60 degrees to about 15 degrees.
 8. The apparatus of claim 7 wherein the first interface angle is about 50 degrees.
 9. The apparatus of claim 7 wherein the first interface is an uphole interface.
 10. The apparatus of claim 1 wherein the circumferentially spaced leaf spring beam members of the locator cage are supported a solid tubular portion of the housing's opposing ends.
 11. The apparatus of claim 1 wherein the reinforcement cage is circumferentially fixed with respect to the locator cage.
 12. The apparatus of claim 11 further comprising: a delimit pin extending from the reinforcement cage radially outwardly into the locator slot, for preventing the reinforcement cage from rotating with respect to the locator cage.
 13. The apparatus of claim 1 wherein the leaf spring beam members of the locator cage and each reinforcement cage are radially aligned.
 14. The apparatus of claim 1 wherein a radially outwardly directed spring force of the locator dogs comprises an aggregated radial spring force exerted by stacked leaf spring beam members of the locator cage and each reinforcement cage.
 15. The apparatus of claim 14 wherein the dogs drag along the casing string when not located in the annular recess.
 16. Apparatus conveyed downhole for releasably locating an annular recess along a casing string in a wellbore comprising: an uphole sub and a downhole sub; a tubular beam locator cage having a locator bore, opposing uphole and downhole ends, and a plurality of radially flexible, leaf spring locator beam members, extending axially between each opposing end, and spaced circumferentially from each other by locator slots, each locator slot terminating axially inward of the housing's opposing ends, each locator leaf spring beam member having a locator dog extending radially outwardly therefrom and intermediate therealong and adapted for engaging the annular recess, the uphole end of the locator cage connected to the uphole sub, and the downhole end of the locator cage being connected to the downhole sub; and at least a first tubular reinforcement cage fit concentrically within the locator bore and axially delimited and sandwiched to float axially between the uphole and downhole subs, each reinforcement cage having a plurality of radially flexible spring reinforcement beam members extending along the axial direction, spaced circumferentially from each other by slots, wherein each locator beam member is supported by at least one reinforcement beam member for providing an aggregated radial spring force at the locator dogs.
 17. Apparatus conveyed downhole for releasably locating an annular recess along a casing string in a wellbore comprising: an uphole sub and a downhole sub; a tubular beam locator cage of locator beams connected at an uphole end to the uphole sub and a downhole end connected to the downhole sub, a recess locator dog extending radially outwardly intermediate along the locator cage, at least a first tubular reinforcement cage of reinforcing beams fit concentrically to, and delimited axially, within the locator cage wherein each locator beam is supported radially by a reinforcement beam of the at least one reinforcement cage for providing an aggregated radial spring force at the recess locator dogs, wherein wherein upon radial displacement of the locator beam loading an axial spacing of the uphole and downhole subs changes and axial length of the reinforcement cage is unconstrained 